Hybrid automatic repeat request method of a downlink tunnel

ABSTRACT

The invention discloses a hybrid automatic repeat request method of a downlink tunnel connection in a multi-hop relay system. The base station transmits tunnel data, comprising of protocol data, to the access relay station via the tunnel link, and receives feedback until the access relay station receives the data correctly. The access relay station analyzes the protocol data unit of each mobile station, transmits the protocol data to the corresponding mobile station, and performs the corresponding process after receiving the feedback from each mobile station. Each hop relay station, except for the station accessing the mobile station, will not transmit the reception acknowledgment information to the base station immediately. The corresponding processing after the access relay station receives the feedback is transmitting the feedback from the mobile station to the base station or, not transmitting the feedback, but applying for bandwidth for retransmission according to the feedback of the mobile station.

This application is a continuation of U.S. application Ser. No.12/734,164 filed Apr. 15, 2010, which application is incorporated hereinby reference for all purposes.

TECHNICAL FIELD

The present invention relates generally to the field of communications,and relates more specifically to a hybrid automatic repeat requestmethod of a downlink tunnel connection in a multi-hop relay system.

BACKGROUND

In order to enlarge the coverage of communication systems and toincrease capacity of systems, one or more relay stations (Relay Station,shortened as RS) may be set between a multi-hop relay base station(Multi-hop Relay Base Station, shortened as MR-BS) and mobile stations(Mobile Stations, shortened as MS). Channel resource allocation must beimplemented by an MR-BS in a centralized relay system, therefore thedesign of a hybrid automatic repeat request (Hybrid Automatic RepeatRequest, shortened as HARQ) of the relay system that schedules a RS in acentralized manner is relatively complex.

The form of an HARQ will be increased accordingly due to theintroduction of an RS, and the typical forms are an end-to-end HARQ andan hop-by-hop HARQ. With regard to the end-to-end HARQ of thecentralized relay, an uplink control station has allocated acorresponding feedback channel for each RS to transfer an ACK/NACKbefore the RS transmits a certain HARQ burst (also called sub-burst). Inexisting technologies, the RS knows the feedback channel allocated toitself by calculation after receiving the burst which is to betransferred, and then transmits feedback over corresponding resource.Once the burst fails to be transferred by the relay, a delay forretransmission may also become large due to the long feedback timebecause air interface resource must be allocated by the MR-BS whencentralized scheduling is adopted.

Moreover, as shown in FIG. 1, when one RS applies access to multipleMSs, one relay tunnel can be set up between the access RS and the MR-BS.Protocol data units (shortened as PDUs) of multiple MSs can make up onetunnel burst by the MR-BS to act as a basic unit of the HARQ to betransmitted in one frame. After the tunnel burst reaches the access RSsuccessfully, the RS restores the PDUs of each MS, and continues toaccomplish the HARQ on the access link.

Presently, in the IEEE802.16j standard draft, the tunnel data can bedivided into two modes: a tunnel packet mode and a tunnel burst mode. Inthe tunnel packet mode, the PDU of each MS is assembled as one tunnelpacket to be transmitted. The tunnel packet has its own packet header(including a Tunnel Connection Identifier (Tunnel CID, shortened asTCID)) and a Cyclic Redundancy Check (Cyclic Redundancy Check, shortenedas CRC) code. One burst may have tunnel packets on different tunnels. Inthe tunnel burst mode, the TCID is provided in a downlink mapinformation element (DL MAP IE), therefore the tunnel data may be takenas one burst of a physical layer. One burst can only include PDUs of MSson the same tunnel. A reduced connection identifier (RCID) of each PDUis replaced by the same TCID.

However, an HARQ method completely involving tunnel data transmission isnever prescribed in existing technologies. For example, an ACK of eachMS cannot be transferred on a tunnel individually when a tunnel packetor a tunnel burst is used for transmission. The advantage of tunneltransmission may be lost if a TCID is not added to tunnel data while adata burst of each MS is fed back individually, because at this moment,it may seem that multiple MSs perform the HARQ independently.

SUMMARY

Whereas the above-mentioned one or more problems, the present inventionprovides a hybrid automatic repeat request method of a downlink tunnel.

According to embodiments of the present invention, the hybrid automaticrepeat request method of a downlink tunnel comprises the followingsteps: a base station transmits tunnel data comprising protocol dataunits of multiple MSs to an access relay station via a tunnel link; theaccess relay station determines its own reception of the tunnel datacomprising protocol data units of multiple MSs, and transmits feedback(reception acknowledgement information or repeat request information) tothe base station via the tunnel link, or receives feedback from each MSabout reception of a corresponding protocol data unit which is sent viaan access link, then according to the feedback from each MS, applies forbandwidth for retransmission or concentratedly transmits the feedbackfrom each MS to the base station via the tunnel link, wherein, theaccess relay station extracts the protocol data unit of each MS aftersuccessfully receiving the tunnel data comprising the protocol dataunits of multiple MSs, and transmits the protocol data unit of each MSto each MS via the access link. The tunnel link is made up of multi-hoprelay stations, the relay station accessing the base station is the1^(st) hop relay station, and the relay station accessing the MS is then^(th) hop relay station, wherein, the 1^(st) hop, the 2^(nd) hop, . . ., the (n−1)^(th) hop relay station will not transmit feedbackimmediately to the base station after receiving the tunnel data.

Wherein, the base station may allocate corresponding channels for datatransmission and feedback to each hop relay station before transmittingthe tunnel data. Each hop relay station may know the feedback channelwhich is allocated to it by the base station via its own calculation.

Wherein, when the t^(th) hop relay station on the tunnel link fails toreceive the tunnel data comprising protocol data units of multiple MSs,the t^(th) hop relay station may transmit repeat request information tothe base station via the (t−1)^(th) hop, the (t−2)^(th) hop, . . . , the1^(st) hop relay station over the feedback channel which is allocated toit by the base station.

If the tunnel end point (i.e., the access relay station) receives thetunnel data comprising protocol data units of multiple MSs successfully,the tunnel end point may feed back upwards reception acknowledgementinformation immediately. If the access relay station fails to receivethe tunnel data comprising protocol data units of multiple MSs, then theaccess relay station may feed back upwards repeat request informationimmediately. The repeat request information may be encoded to inform thebase station that in which hop a reception error of the tunnel dataoccurs.

If the t^(th) relay station receives the tunnel data comprising protocoldata units of multiple MSs in the i^(th) frame correctly, the t^(th)relay station may transfer feedback from a downlink relay station to thebase station in the (i+m)^(th) frame, wherein, m=M*q+(M+1)*k, M is thenumber of hops between the t^(th) hop relay station and the tunnelend-point relay station, q is the number of fixed delay frames of eachhop relay station for the tunnel data, k is a delay for hybrid automaticrepeat request feedback for the tunnel data on each hop relay station.If the feedback received is reception acknowledgement information, thet^(th) hop relay station transfers uplink without any change. If thefeedback received is repeat request information, the t^(th) hop relaystation may, by encoding the repeat request information, inform the basestation that in which hop a reception error of the tunnel data occurs.

If the t^(th) hop relay station fails to receive the tunnel datacomprising protocol data units of multiple MSs, the t^(th) hop relaystation may feed back upwards repeat request information over thefeedback channel which is allocated to it by the base station. Therepeat request information may be encoded to inform the base stationthat in which hop a reception error of the tunnel data occurs.

If the tunnel data comprising protocol data units of multiple MSs is atunnel burst, the t^(th) hop relay station that has received the tunnelburst may determine whether it receives the protocol data unit of eachMS successfully according to a cyclic redundancy check code which iscarried by the protocol data unit of each MS. The encoded repeat requestinformation may include information with respect to the t^(th) hop relaystation and information with respect to connections of which protocoldata units are not received successfully by the t^(th) hop relaystation.

If the tunnel data comprising protocol data units of multiple MSs is atunnel packet, the t^(th) hop relay station that has received the tunnelburst may determine whether it receives the tunnel data comprisingprotocol data units of multiple MSs successfully according to a cyclicredundancy check code of the tunnel data comprising protocol data unitsof multiple MSs. The encoded repeat request information may includeinformation with respect to the t^(th) hop relay station and informationwith respect to connections in the tunnel packet that are not receivedsuccessfully.

If the access relay station receives the tunnel data comprising protocoldata units of multiple MSs successfully, the access relay station maytransmit the protocol data unit of each MS to each MS respectively.

Here, each MS may transmit the reception of the corresponding protocoldata unit to the access relay station, i.e. suspending the hybridautomatic repeat request on the access link. The access relay stationmay retransmit the corresponding protocol data unit to the MS whichfails to receive the corresponding protocol data unit via pre-scheduledair interface resource. In the event that the pre-scheduled airinterface resource is insufficient for retransmitting the correspondingprotocol data unit to the MS which fails to receive the correspondingprotocol data unit, the access relay station may apply again to the basestation for the air interface resource for retransmission.

Moreover, the access relay station may also report the reception of theprotocol data units at multiple MSs upwards to the base station in acentralized report manner to complete the hybrid automatic repeatrequest on the access link. Here, the access relay station reports thereception of the protocol data units at multiple MSs upwards to the basestation via the feedback channel which is pre-allocated by the basestation. The access relay station may retransmit the correspondingprotocol data unit to the MS which fails to receive the correspondingprotocol data unit via pre-scheduled air interface resource. In theevent that the pre-scheduled air interface resource is insufficient forretransmitting the corresponding protocol data unit to the MS whichfails to receive the corresponding protocol data unit, the access relaystation applies again to the base station for the air interface resourcefor retransmission.

According to the present invention, a hybrid automatic repeat requestmethod including the tunnel data transmission can be perfected.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrated here, which constitutes a part ofthis application paper, are used to provide further comprehension of thepresent invention, exemplary embodiments of the present inventiontogether with the descriptions thereof serve to explain the presentinvention, but not constitute inappropriate limitations to the presentinvention. In the drawings:

FIG. 1 is a schematic diagram of a configuration of a wireless relaynetwork according to embodiments of the present invention;

FIG. 2 is a flow chart of a hybrid automatic repeat request method of adownlink tunnel according to embodiments of the present invention;

FIG. 3 is a schematic diagram of downlink tunnel data retransmissionaccording to embodiments of the present invention;

FIG. 4 is a schematic diagram of an HARQ on a link-by-link downlinktunnel adopting pre-scheduling on one access link according toembodiments of the present invention;

FIG. 5 is a schematic diagram of an HARQ on a downlink tunnel accordingto embodiments of the present invention;

FIG. 6 is a schematic diagram of an HARQ on a downlink tunnel adoptingpre-scheduling on one access link according to embodiments of thepresent invention;

FIG. 7 is a schematic diagram of an HARQ on a downlink tunnel accordingto embodiments of the present invention;

FIG. 8 is a schematic diagram of an example of centralized feedbackcodes according to embodiments of the present invention;

FIG. 9 illustrates a classification of a CID of tunnel data according toembodiments of the present invention;

FIG. 10 is a schematic diagram of an example of tunnel packet feedbackencoding according to embodiments of the present invention;

FIG. 11 is a schematic diagram defining an empty burst mode according toembodiments of the present invention;

FIG. 12 is a schematic diagram defining an empty burst format accordingto embodiments of the present invention;

FIG. 13 is a schematic diagram defining a feedback delay notice modeaccording to embodiments of the present invention; and

FIG. 14 is a schematic diagram of a feedback delay notice formataccording to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described below indetail with reference to the drawings.

Referring to FIG. 1, a configuration of a wireless relay networkaccording to embodiments of the present invention is illustrated. Asshown in FIG. 1, RS3 accesses multiple MSs, accordingly, one relaytunnel may be set up between the RS3 and a MR-BS. Protocol Data Units(PDU) of multiple MSs may make up one tunnel burst by the MR-BS to actas a basic unit of an HARQ to be transmitted in one frame. After thetunnel burst reaches the RS3 successfully, the RS3 restores the PDU ofeach MS, and continues to accomplish the HARQ accomplished on an accesslink.

Referring to FIG. 2, a hybrid automatic repeat request method of adownlink tunnel according to embodiments of the present invention isillustrated. The method includes the following steps: S202, a basestation transmits tunnel data comprising protocol data units of multipleMSs to an access relay station via a tunnel link, and receives feedbackfrom a relay station until the access relay station receives datacorrectly; S204, the access relay station extracts the protocol dataunit of each MS from the tunnel data, transmits the protocol data unitof each MS to the corresponding MS, and performs correspondingprocessing after receiving feedback from each MS. Wherein, the tunnellink is made up of multi-hop relay stations, the relay station accessingthe base station is the 1^(st) hop relay station, and the relay stationaccessing the MS is the n^(th) hop relay station, wherein, the 1^(st)hop, the 2^(nd) hop, . . . , the (n−1)^(th) hop relay station will nottransmit reception acknowledgement information to the base stationimmediately after receiving the tunnel data. Wherein, the correspondingprocessing is, after the access relay station receives the feedback fromeach MS, uplink relaying the feedback from the MSs to the base stationor not uplink relaying the feedback but applying for bandwidth forretransmission according to the feedback from the MSs.

The processing of the above steps will be described hereinafter indetail.

In Step S202, as shown in FIG. 3, the RS is not required to providefeedback immediately after receiving the tunnel data, but continues totransfer the data. The MR-BS has allocated a corresponding feedbackchannel for each RS to transfer the feedback (tunnel data ACK/NAK)before the RS transmits certain tunnel data. Each RS may know thefeedback channel allocated to itself by its own calculation, andtransmits the feedback over corresponding resource. Here, the feedbackfrom the RS3 is not received from the MS, but is generated locally fromitself. There is no need to consider the access link in the calculationof the feedback time of all RSs.

The regulation for calculating a feedback delay for an end-to-end tunnelburst HARQ is provided by the following formula: m=M*q+(M+1)*k Wherein,M is the number of hops between the RS and the tunnel end point; q isthe number of fixed delay frames of the RS for the tunnel burst; k isthe delay for the HARQ feedback for the tunnel burst defined by thesystem, which may be provided in system broadcast information dependingon the situation.

Wherein, the specific implementation may use, but is not limited to thefollowing method: adding the number of hops between each station and thetunnel end point to the field of the number of hops (hop depth) of thesub-burst information element (IE) of the tunnel data. Each station onthe tunnel calculates the time for transferring the tunnel feedback byapplying the value M to the above formula.

Moreover, if the RS does not transfer the tunnel burst successfully, itis necessary to feed back the failure over the pre-arranged feedbackchannel. The MR-BS restarts to schedule the next transfer. This stepwill end if and only if the tunnel data reaches the access RSsuccessfully. Accordingly, it is necessary to define encoded feedback todenote different situations of the tunnel data transmission.

As shown in FIG. 4, when the tunnel data fails to be transmitted on thelink, the encoded tunnel data NAK should be fed back to the MR-BSaccording to the pre-scheduling of the MR-BS. According to the codes,the MR-BS determines the RS that has failing transmission, and schedulescorresponding resource to retransmit the failed tunnel data.

When the tunnel data is a tunnel packet, a CRC check code is added tothe packet itself. The RS may determine whether the reception issuccessful according to the CRC check code of the packet. If the tunnelpacket fails to be received, the entire tunnel packet may beretransmitted. The MR-BS is required to allocate only half a sub-channelfor the tunnel packet feedback as a feedback channel, it is equivalentto take one tunnel packet as one ordinary sub-burst, the feedbackchannel is saved greatly, but the cost is that data channels forretransmission always occupy the tunnel packet size. The feedback on theNAK of the tunnel packet is only required to reflect that in which hopthe failure occurs, and the corresponding codes may be shown as FIG. 8.The feedback code D0 indicates that the tunnel packet is transmittedsuccessfully. Each relay transmits D0 to the MR-BS without any changeafter receiving D0. If the tunnel data fails to be transmitted in thex^(th) hop, the start point of this hop, RSx, will transmit D1, RS(x−1)receiving D1 will add one to the code, and then transmits D2. Throughcycling like this, the MR-BS may know that it is necessary to re-arrangeresource to transmit the tunnel packet in the x^(th) hop when receivingthe feedback encoded as a Dx.

Furthermore, the MR-BS may also arrange a corresponding feedback channelfor each connection in the tunnel packet. Here, the advantage of thetunnel packet is that if the tunnel burst is transmitted successfully,it may be checked out at one time that all PDUs are transmittedsuccessfully by using the CRC carried by the packet itself, and then allthe connections are required to feed back codes which represent successover their own feedback channels. Correspondingly, if the tunnel burstfails to be transmitted, the RS shall check out the connection that hasan error transmission according to the CRC check code carried by eachPDU itself, and then transmits feedback using codes in the existing 16jstandard. After receiving the feedback code in the existing standard,the MR-BS will arrange retransmission of the tunnel packet according tothe feedback. The retransmitted packet will only carry the PDU of theconnection that had an error transmission last time. In this way, thefeedback channel will be enlarged, but the overhead of the datatransmission channel will be reduced.

When the tunnel data is a tunnel burst, the burst itself does not carrythe CRC check code. The RS should determine respectively whether the PDUis received successfully according to the CRC check code carried by eachPDU itself which constitutes the tunnel burst, and finally, determineswhether the entire burst is received successfully. If the failure ofreceiving a part of PDUs leads to the failure of receiving the tunnelburst, it is only required to retransmit the corresponding PDU,therefore, the feedback code of the tunnel burst is required not only toreflect the hops in which the failure occurs, but also to reflect thePDU of the connection in which the failure occurs. Therefore, thefeedback channel of the tunnel burst is actually the collection offeedback channels of all connections on the tunnel. Each sub-burstmaking up the burst may feed back its reception using the codes shown inFIG. 8. The RS collects the feedback from each sub-burst of the tunnelburst, and concentratedly transmits the feedback over the feedbackchannel which is allocated by the base station. The MR-BS will arrangeretransmission of the tunnel burst according to the feedback afterreceiving the existing centralized feedback codes. The retransmittedburst will only carry the sub-burst corresponding to the PDU of theconnection which had an error transmission last time.

Moreover, in the existing IEEE802.16j standard technology, each MS(distinguished by a RCID) can only carry 16 connections at most andaccordingly has 16 sub-channels, therefore 4 bits may be used toconstitute a feedback subchannel identifier (ACID). However, in thetunnel burst, RCIDs of different sub-bursts are replaced by the sameTCID, the ACID of each MS may conflict at this moment, and moreover itcan not be identified that which sub-burst has an error. Therefore, asshown in FIG. 9, the tunnel packet TCID and the tunnel burst TCID ofbursts may be defined in section in the TCID definition. In this way,the tunnel packet mode and the tunnel burst mode can be distinguished bythe TCID in transmission. In the tunnel packet mode, the ACID of thecorresponding sub-burst is still 4 bits. In the tunnel burst mode, theACID of the corresponding sub-burst is defined as 8 bits and is sortedagain, in this way the conflict of the ACIDs can be avoided.

In Step S204, the access RS (the start point of the access link) hasstored the burst on each access link, and the MR-BS should arrange thechannels for burst retransmission and feedback on the access link.

The characteristic of the embodiment 1 is a link-by-link HARQ, theso-called link-by-link, as shown in FIG. 1, means that the tunnel HARQis one link and each access link between the access RS at the tunnel endpoint and each MS is another link. The data is transmitted overtransmission links which are made up of two links respectively indifferent combination formats. The transmission over the two linksrespectively adopts an end-to-end HARQ. In this way, new data may beginto be transmitted as long as the tunnel end point receives the tunneldata successfully. Compared to the case where the MR-BS can transmit newdata only if it receives feedback from the MS, the efficiency of datatransmission is obviously improved in the embodiment of the presentinvention.

In the embodiment 1, the feedback on the access link is only required tobe transmitted to the access RS. However, if the burst transmissionfails on the access link, the access RS must apply for bandwidthretransmission and give feedback to the MR-BS. In order to improve theretransmission efficiency of the access link, it may be considered toadopt pre-scheduling on the access link.

As shown in FIG. 4, the MR-BS may pre-schedule appropriate air interfaceresource for retransmission on the access link according to linkinformation of the access link. In case the MS reports to the uplink RS3that a burst fails to be received on the access link, the RS3 may beginto retransmit the failed burst immediately on the pre-scheduled airinterface resource, without waiting the MR-BS to arrange new airinterface resource. The pre-scheduled resource (i.e., pre-scheduling thenumber of times of retransmission as well as sub-channels forretransmission) may be adjusted according to channel informationreported upwards by the access link.

If all bursts on the access link are transmitted successfully before thepre-scheduling resource is exhausted, the access RS need not feed backagain. If some bursts of the MS are still not transmitted successfullyafter the pre-scheduling resource is exhausted, the access RS must applyresource to the MR-BS for retransmitting the failed bursts. Thisapplication may use an HARQ error report message defined by theIEEE802.16j standard in the existing technology.

The characteristic of the embodiment 2 is link-by-link transmission, andthat feedback about the MS burst may be transmitted to the MR-BS. Asshown in FIG. 5, the MS burst may begin to be transmitted only after thetunnel link data is transmitted successfully. ACKs/NAKs of all MSs arecollected by the access RS, and then are fed back to the uplink RSconcentratedly, and finally are transferred to the MR-BS. The MR-BSschedules the resource and arranges to retransmit the failed MS burstaccording to the received feedback.

The characteristic of the embodiment 3 is that feedback about the MSburst may be transmitted to the MR-BS and that the MR-BS may pre-arrangea transmission link from the MR-BS to the MS (as shown in FIG. 7). Ifthe tunnel data is transmitted to the RS3 without retransmission and arereceived by the RS3 successfully, the MS burst in the tunnel data may betaken out by the RS3 immediately and be transmitted to the MS. But thecost is that pre-arranged resource will be wasted in case the tunneldata is not transmitted successfully.

For the embodiment 2 and embodiment 3, as shown in FIG. 6, in order toimprove the retransmission efficiency, the MR-BS may pre-scheduleappropriate air interface resource for retransmission on the access linkaccording to the link information of the access link. In case the MSreports that the burst fails to be received on the access link, theretransmission may begin immediately on the pre-scheduled air interfaceresource without waiting the MR-BS to arrange new air interfaceresource. After the pre-scheduled resource is exhausted, the access RSmust, after collecting every result of retransmission based on thepre-scheduled resource on the access link, report them upwards to theMR-BS no matter whether the retransmission is successful.

For the embodiment 2 and embodiment 3, the manner of reporting thecentralized feedback may use, but is not limited to the followingmanners. The MR-BS may arrange one dedicated HARQ_ACKCH area for theaccess RS to report the centralized feedback. The sequence of thefeedback in the area may be designated by the MR-BS according to thesequence of the connections or bursts, or may also adopt an encodingmanner. An encoding manner of the centralized feedback is shown in FIG.10, the feedback of three bursts in this figure may be encoded in onegroup, and is denoted by three tiles defined in the IEEE 802.16jstandard. The combinations of different codes are orthogonal to eachother, and denote different situations of MS burst transmission. Forexample, the feedback code A0 denotes that three bursts are all receivedcorrectly, and the feedback code A1 denotes that an error transmissionof the first burst in low bits occurs on the access link while the othertwo bursts are received correctly.

For the embodiment 2 and embodiment 3, it is required to trigger the RSto transfer the centralized feedback when the centralized feedback isreported. But in the existing technology, the RS may be triggered onlywhen it receives the data that is to be transferred. It is not definedin the existing technology regarding to how to trigger the RS totransfer the feedback when the burst is retransmitted on the access linkbut the RS fails to receive the data. In order to resolve the problem,specific methods may include, but is not limited to, the two methods asbelow.

Method One is using empty data to trigger. An empty burst, HARQ burst,is defined in FIG. 11, and the burst format of the empty burst, HARQburst, is defined in FIG. 12.

The so-called empty data refer to the data without any datatransmission. For the embodiment 2 and embodiment 3, there are severalempty bursts in one empty data. The centralized feedback is thecollection of the corresponding empty bursts. The RS which receives theempty data only calculates the delay for the feedback about transferringthe empty data. A formula for calculating the delay is given as follows:

if the RS receives the empty data in the i^(th) frame, the feedbackshould be given in the (i+n)^(th) frame, wherein, n is determined by theformula (1).

n=H*p+(H+1)*j+s  (2)

in the formula (2), H is the number of the hops between the RS and theend point of the link, p is the number of fixed delay frames of the RS,j is a feedback delay for the HARQ defined by the system and is providedin a system broadcast message; s is a delay for the access RS collectingfeedback from all RSs.

Method Two is notifying the RS directly of the delay required fortransferring the feedback. The notice mode of the feedback delay isdefined in FIG. 13. The notice format of the feedback delay is definedin FIG. 14. The RS which receives the notice will wait for thecorresponding time according to the delay information in the notice andthen transfers the feedback from the designated connection directly.

The above descriptions are just embodiments of the present invention andare not used to limit the present invention, for those skilled in theart, various modifications and variations can be made to the presentinvention. Any modification, equivalent substitution or improvement,etc. within the spirit and principle of the present invention shall beincluded in the scope of claims of the present invention.

1. A hybrid automatic repeat request method of a downlink tunnel,comprising the following steps: a base station transmitting tunnel datathat comprise protocol data units of multiple mobile stations to anaccess relay station via a tunnel link; (a) the access relay stationdetermining its own reception of the tunnel data that comprise protocoldata units of multiple mobile stations, and transmitting feedback to thebase station via the tunnel link; or (b) the access relay stationreceiving feedback from each of the mobile stations about reception of acorresponding protocol data unit which is sent via an access link, andaccording to the feedback from each of the mobile stations, applying forbandwidth for retransmission or concentratedly transmitting the feedbackfrom each of the mobile stations to the base station via the tunnellink, wherein the access relay station extracting the protocol data unitof each of the mobile stations after successfully receiving the tunneldata that comprise protocol data units of multiple mobile stations, andtransmitting the protocol data unit of each of the mobile stations toeach of the mobile stations via the access link, the tunnel link beingmade up of multi-hop relay stations, the relay station accessing thebase station being the 1^(st) hop relay station, and the relay stationaccessing the mobile station being the n^(th) hop relay station,wherein, the 1^(st) hop, the 2^(nd) hop, . . . , the (n−1)^(th) hoprelay station not transmitting feedback immediately to the base stationafter receiving the tunnel data.
 2. The method according to claim 1,wherein, the base station allocates corresponding channels for datatransmission and feedback to each of the hop relay stations beforetransmitting the tunnel data.
 3. The method according to claim 2,wherein, each of the hop relay stations knows the feedback channelallocated to it by the base station via its own calculation.
 4. Themethod according to claim 3, wherein, when the t^(th) hop relay stationon the tunnel link fails to receive the tunnel data that compriseprotocol data units of multiple mobile stations, the t^(th) hop relaystation transmits repeat request information to the base station via the(t−1)^(th) hop, the (t−2)^(th) hop, . . . , the 1^(st) hop relay stationon the feedback channel which is allocated to it by the base station. 5.The method according to claim 4, wherein, if the t^(th) relay stationreceives the tunnel data that comprise protocol data units of multiplemobile stations in the i^(th) frame, then the t^(th) relay stationtransmits feedback from a downlink relay station to the base station inthe (i+m)^(th) frame, wherein, m=M*q+(M+1)*k, M is the number of hopsbetween the t^(th) hop relay station and the access relay station, q isthe number of fixed delay frames of each of the hop relay stations forthe tunnel data that comprise protocol data units of multiple mobilestations, k is a delay for hybrid automatic repeat request feedback forthe tunnel data that comprise protocol data units of multiple mobilestations on each of the hop relay stations.
 6. The method according toclaim 4, wherein, the t^(th) relay station encodes the repeat requestinformation, and transmits encoded repeat request information to thebase station via the feedback channel which is allocated to it by thebase station.
 7. The method according to claim 5, wherein, if the accessrelay station receives the tunnel data that comprise protocol data unitsof multiple mobile stations successfully, then the access relay stationtransmits reception acknowledgement information to the base stationimmediately, otherwise encodes the repeat request informationimmediately, and transmits the encoded repeat request information to thebase station.
 8. The method according to claim 7, wherein, if the tunneldata that comprise protocol data units of multiple mobile stations is atunnel burst, then the t^(th) hop relay station determines whether itreceives the protocol data unit of each of the mobile stationssuccessfully according to a cyclic redundancy check code which iscarried by the protocol data unit of each of the mobile stations itself.9. The method according to claim 8, wherein, the encoded repeat requestinformation includes information with respect to the t^(th) hop relaystation and information with respect to connections of which theprotocol data units are not received successfully by the t^(th) hoprelay station.
 10. The method according to claim 9, wherein, the accessrelay station retransmits the corresponding protocol data unit to themobile station which fails to receive the corresponding protocol dataunit via pre-scheduled air interface resource.
 11. The method accordingto claim 10, wherein, when the pre-scheduled air interface resource isinsufficient for retransmitting the corresponding protocol data unit tothe mobile station which fails to receive the corresponding protocoldata unit, the access relay station applies again to the base stationfor the air interface resource for retransmission.
 12. The methodaccording to claim 11, wherein, the access relay station transmits thefeedback from the multiple mobile stations concentratedly to the basestation via the tunnel link or a dedicated hybrid automatic repeatresponse link.
 13. The method according to claim 7, wherein, if thetunnel data that comprise protocol data units of multiple mobilestations is a tunnel packet, then the t^(th) hop relay stationdetermines whether it receives the tunnel data that comprise protocoldata units of multiple mobile stations successfully according to acyclic redundancy check code of the tunnel data that comprise protocoldata units of multiple mobile stations.
 14. The method according toclaim 13, wherein, the encoded repeat request information includesinformation with respect to the t^(th) hop relay station.
 15. The methodaccording to claim 14, wherein, the access relay station retransmits thecorresponding protocol data unit to the mobile station which fails toreceive the corresponding protocol data unit via pre-scheduled airinterface resource.
 16. The method according to claim 15, wherein, whenthe pre-scheduled air interface resource is insufficient forretransmitting the corresponding protocol data unit to the mobilestation which fails to receive the corresponding protocol data unit, theaccess relay station applies again to the base station for the airinterface resource for retransmission.
 17. The method according to claim16, wherein, the access relay station transmits the feedback from themultiple mobile stations to the base station via the tunnel link or aspecial hybrid automatic repeat response link.
 18. The method accordingto claim 6, wherein, if the access relay station receives the tunneldata that comprise protocol data units of multiple mobile stationssuccessfully, then the access relay station transmits receptionacknowledgement information to the base station immediately, otherwiseencodes the repeat request information immediately, and transmits theencoded repeat request information to the base station.
 19. The methodaccording to claim 18, wherein, if the tunnel data that compriseprotocol data units of multiple mobile stations is a tunnel burst, thenthe tth hop relay station determines whether it receives the protocoldata unit of each of the mobile stations successfully according to acyclic redundancy check code which is carried by the protocol data unitof each of the mobile stations itself.
 20. The method according to claim19, wherein, the encoded repeat request information includes informationwith respect to the t^(th) hop relay station and information withrespect to connections of which the protocol data units are not receivedsuccessfully by the t^(th) hop relay station.
 21. The method accordingto claim 20, wherein, the access relay station retransmits thecorresponding protocol data unit to the mobile station which fails toreceive the corresponding protocol data unit via pre-scheduled airinterface resource.
 22. The method according to claim 21, wherein, whenthe pre-scheduled air interface resource is insufficient forretransmitting the corresponding protocol data unit to the mobilestation which fails to receive the corresponding protocol data unit, theaccess relay station applies again to the base station for the airinterface resource for retransmission.
 23. The method according to claim22, wherein, the access relay station transmits the feedback from themultiple mobile stations concentratedly to the base station via thetunnel link or a dedicated hybrid automatic repeat response link. 24.The method according to claim 18, wherein, if the tunnel data thatcomprise protocol data units of multiple mobile stations is a tunnelpacket, then the t^(th) hop relay station determines whether it receivesthe tunnel data that comprise protocol data units of multiple mobilestations successfully according to a cyclic redundancy check code of thetunnel data that comprise protocol data units of multiple mobilestations.
 25. The method according to claim 24, wherein, the encodedrepeat request information includes information with respect to thet^(th) hop relay station.
 26. The method according to claim 25, wherein,the access relay station retransmits the corresponding protocol dataunit to the mobile station which fails to receive the correspondingprotocol data unit via pre-scheduled air interface resource.
 27. Themethod according to claim 26, wherein, when the pre-scheduled airinterface resource is insufficient for retransmitting the correspondingprotocol data unit to the mobile station which fails to receive thecorresponding protocol data unit, the access relay station applies againto the base station for the air interface resource for retransmission.28. The method according to claim 27, wherein, the access relay stationtransmits the feedback from the multiple mobile stations to the basestation via the tunnel link or a special hybrid automatic repeatresponse link.